Pebble heater apparatus



Dec. 12, 1950 I, J. WEBER PEBBLE HEATER APPARATUS 2 Sheets-Sheet 1 Filed Nov. 21, 1947 oooooooooo o v O 0000 OOOOOOV VD V o o 4 4 o oooo o ov v INVENTOR. L J WEBER FIG. I

ATTOR/VE VS L. J. WEBER "PEBBLE mm APPARATUS Dec. 12, 1950 2 Sheets-Sheet 2 Filed Nov. 21, 1947 FIG 3 36 mmvrox.

L. J. WEBER BY, @QAJMJW A T7'0RNEYS REACTOR Patented Dec. 12, 1950 PEBBLE HEATER APPARATUS Louis J. Weber, Bartlesville, Okla... assignor to Phillips Petroleum Company, a corporation of Delaware Application November 21, 1947, Serial No. 787,413

7 Claims. 1

This invention relates to pebble heater apparatus. In one of its more specific aspects, it relates to thermal conversion'apparatus. In another of its more specific aspects, it relates to pebble heating or regeneration chambers of pebble heater apparatus.

Thermal conversion processes carried on in socalled pebble heating apparatus utilize a flowing mass of pebbles which is heated to a high temperature in a flrst direct heat exchange step and is then caused to contact gaseous materials, furnishing thereto, in a second direct heat exchange. The conventional pebble heater apparatus comprises two chambers which may be disposed in substantially vertical alignment. Solid heat exchange material, such as refractory pebbles, is introduced into the upper portion of a first chamber. The solid heat exchange material flows downwardly through thechamber in direct heat exchange with a hot gaseous heat exchange material. The solid heat exchange material is heated to a high temperature in such heat exchange and is then passed to a second chamber in which it is caused to contact gaseous materials in a second direct heat exchange relation, furnishing heat thereto.

Most conventional pebble heaters are provided with a combustion chamber adjacent or in close proximit to the lower portion of the first chamber. Hot combustion gas from the combustion chamber is injected through the sides of the first chamber, better known as the pebble heating chamber. Pebbles which pass through the heating chamber contact the rising combustion gas and are heated as above described. One disadvantage of such pebble heater apparatus is that pebbles near the periphery of the pebble bed in the heating chamber are heated to a higher temperature than those in the center of the downwardly flowing bed. This is due to the fact that a greater portion of the combustion gas tends to take the path of least resistance through the pebble bed. In most pebble heater apparatus, pebbles are introduced into the pebble heater chamber through a single opening in its top. Pebbles are withdrawn from a point substantially centrally located in the area of the heating chamber. As pebbles flow through the chamber they tend to form an inverted cone, downwardly and outwardly from the pebble inlet, and the pebbles flowing out of the chamber tend to form a cone downwardly and inwardly toward the pebble outlet. It will be seen that due to the cone shaped top and bottom of the bed, the area near the periphery of the bed is the thinnest downwardly and usually the point of least resistance. Gas tends to pass directly upwardly from the gas inlet, through the periphery of the bed and out of the effluent outlet in the top of the chamber. A portion of the pebble bed below the moving cone of pebbles is relatively stagnant. Once these pebbles in the stagnant area are heated they lose very little of their heat and thus receive very little from the gas passing upwardly therethrough. For that reason, gas leaving the heating chamber through the effluent outlet carries with it a considerable amount of heat which could have been imparted to cooler pebbles in the central portion of the chamber.

An object of the invention is to provide an improved chamber for heating pebbles in pebble heater apparatus. Another object is to provide an improved method for heating pebbles in pebble heating apparatus. Another object is to provide an improved combustion chamber for a pebble heater. Another object is to provide improved means for supporting a pebble bed within heating chambers of pebble heater apparatus. Another object is to provide improved communication means between heating and conversion chambers of pebble heater apparatus. Another object is to provide means for more evenly heating a given cross section of a flowing pebble bed in such a heating chamber. Other and further objects will be apparent to those skilled in the art on reference to the accompanying discussion, drawings and the claims.

The term pebble, as used herein, denotes any solid refractory material of flowable form, size, and strength which is suitable to carry large amounts of heat from the pebble heating chamber to the gas heating chamber. Pebbles conventionally used in pebble heater apparatus are substantially spherical in shape and are from about one-eighth inch to about one inch in diameter. In high temperature processes, pebbles having a diameter of approximately threeeighths inch are preferred. The pebbles must be formed of a refractory'material which will withstand temperatures at least as high as the highest temperature attained in the pebble heating chamber. The pebbles must also be capable of withstanding temperature changes within the apparatus. A refractory material, such as a metal, ceramic, or other satisfactory material may be utilized to form such pebbles. Satisfactory pebbles may be formed of silicon carbide, alumina, periclase, beryllia, Stellite, zirconia and mullite in admixture with each other or with othtt materials. Pebbles formed of such materials, when properly fired, serve very well in high temperatures, some withstanding temperatures up to about 3500 F. Pebbles which are inert or catalytic may be used in any selected process.

Understanding of the invention will be facilitated upon reference to the attached drawings in which Figure 1 is a diagrammatic partial section view of a pebble heating chamber embodying the invention. Figure 2 is a plan View taken on the line 2-2 of Figure 1 with a portion of the baffle cut away. Figure 3 is a top view of a brick of the type used in the construction of the dome shown in Figures 1 and 2. Figure 4 is a side view of such a brick. Figure 5 is a schematic view of a pebble heater apparatus showing the relation between pebble heating and reactor chambers and the path of pebble recycle.

.In Figure 1, shell H is closed at its ends by closure members I2 and [3. The walls of shell ii are lined with insulating means such as common refractory materials 14 and super-refractory materials l5 backed by common refractory materials. Common refractory materials may include block insulation, insulating fire brick and fire clay fire brick or layers of any two or all of them. Super-refractory materials [5 may be silicon carbide, mullite, or alumina or any other suitable refractory having physical and chemical properties which give it sufiicient strength to withstand heavy loads and high temperature without substantial breakage or deterioration. Silicon carbide may be satisfactorily used in operations utilizing temperatures up to about 3000 F. Mullite can be satisfactorily used up to about 3000 F. and alumina may be satisfactorily used at temperatures up to about 3300 F. The above materials may be used at those temperatures without substantial oxidation or reaction with most conventionally used pebbles. Superrefractory material I5 is positioned so as to form an inner lining in the lower portion of shell Ii. Layers of common refractory and super-refractory materials are also provided to insulate the bottom of said shell.

Dome I6 is provided within shell ii at a point intermediate its ends and intermediate the inner insulation lining of super-refractory material therein. Dome I6 is preferably constructed of super-refractory bricks 11, which are formed in a plurality of self-supporting rings.

taper inwardly on all four sides from top to bottom. Two of the sides are grooved so that when a brick is fitted with an adjacent brick the grooves form communication means from the space below to the space above said dome. The other two sides are curved from side to side, one being convex and the other concave. A first pebble conduit means, such as refractory throat i8, is provided substantially centrally in said dome and extends a short spaced distance upwardly into a heating zone, formed above said dome, and downwardly a short spaced distance into a combustion zone, formed below said dome. Throat I8 is preferably constructed of a plurality of elongated super-refractory sections 19. When assembled throat [8 has a tubular opening extending centrally therethrough which is substantially coaxial with shell I I. The outer surface of throat I8 is tapered so as to substantially coincide with the faces of the bricks comprising the inner ring of refractory dome l6. Dome l6, as so constructed, is not only self-supporting but is capable of supporting a load of at least 1000 pounds per square foot at operating temperatures These bricks are constructed in the form of plugs which while expanded by such operating temperatures. Extending upwardly through the bottom of the chamber, formed by shell H and closure members I 2 and I3, is a second pebble conduit means 23, at least a portion of which is preferably constructed of a. plurality of refractory rings 24 which are provided with tongues on one side and grooves on the other which tongues and grooves reciprocate to hold the rings in a coaxial position. Conduit means 23 extends upwardly through the combustion zone and communicates with throat I8 by means of an expansion joint, formed by a slidable connection between throat l8 and conduit means 23. Conduit means 23 is so formed that a tubular opening of substantially the same diameter as that in throat It extends through its length. The upper inner diameter of means 23 is enlarged so as to allow the insertion of throat l8 thereinto forming the slide joint therebetween. Means, adapted so as to inject combustible materials into the combustion zone formed beneath dome l6 and to burn the combustible materials within said zone, are provided within the lower portion of the heating chamber. Such means preferably comprises burners 25 which are used for injecting and burning such combustible materials within the combustion zone. The combustion zone forms a plenum chamber in which combustion and tempering of the combustion gases takes place. Burners 25 are positioned obliquely so as to inject the combustible materials tangentially into the combustion zone. Burners adapted in upright or other positions or other means for injecting combustion gases into the combustion zone may be satisfactorily used.

Bafile means, such as refractory plate 28, is provided to cover at least a portion of dome l6.

Apertures are left under plate 26 so as to allow the passage of gases inwardly and upwardly underneath the plate and the escape of such gases at the upper end of the plate.

The baffle means may be of any desired size so as to allow the desired opening for the escape of gas in its cen- 3 baffling while at the same time being of sufficient strength to support with the aid of dome it a layer of aggregate materials 21 and a moving bed of pebbles 28 thereabove. Pebble inlet means, such as conduit 29, is provided in the upper portion of the heating chamber preferably extending substantially centrally through closure l3. Combustion gas outlet means, such as conduit 33, is also provided in the upper portion of the heating chamber, preferably in closure member 13. A manhole or access opening 34 is also provided in closure member l3.

Separation means, such as a layer of aggregate material 2?, is provided to cover dome l6 and the baffle means. Alternate separation means such as a refractory cone, may be utilized in place of the layer of aggregate material. Refractory throat l8 should extend upwardly into the heating zone far enough to retain the aggregate material therein and prevent it from falling through the tubular opening therein. One of the purposes of such separation means is to prevent the pebbles from falling through and clogging the perforations within dome 16. Another purpose of such means is to provide a plenum chamber in which the heating gas will become further tempered. The heating chamber may be 5. satisfactorily," operated without such a separation means by proper sizing and positioning of the} baille means, *buthse of= such separation nieans is preferred. Y

In Figure 5, the pebbleheatingchamber con tained withinshell H is disposed substantially vertically above gas heating chamber contained within shell 35 Burners are shownextending into the lower portion or shell I I. Eiiluent outlet meansysuch as conduit 33, extendsfrom the'top of shell I I. "Reaction material inlet means, such asconduit 36, is provided in the lower portion" or shell 35. Efiluent material outlet means, such as conduit 31-, are provided in thetop ofclosed shell 35.- Pebblerecycle mea'nsfsuch as elevator 38,.is provided to transport pebbles from the bottom of thegas heating {chamber-contained with in: closed shell 35to the upper portion of the heating chamber contained within -closed shell In' the operation of the device shown inFig'- ures-l and f the drawings, pebbles made from any selected refractory material, suitable for; the

process to be carried on within theapparatus. are inserted into the upper portion of the heatbustible materials are injected into the heating zone, beneath therefractory dome, through the burners therein. Combustion gas passing from the burners tangentially into the'combustion zone pass in a whirling motion around the combustion zone whilemore complete burnin 'of the combustible material is accomplished. Excess oxygen-containing gasmay be injected for the purpose ot tempering orcontrolling the temperature.;of the combustion gas: The combustion gas, together with any excess oxygen-containing gas, passes upwardly through the perforate dome and is 'directedby the bailie means inwardly toward the axis of the, chamber. As the gas passes from under the baiiie means it rises through the bed of pebbles in direct heat exchange therewith, raising the pebbles to a high temperature. As the combustion gas exits from the top of the pebble bed it escapes from the chamber through outlet 33; The heated pebbles pass downwardlv through the pebble conduit formed by throat i8 and conduit means 23 into the gas heating chamber wi'thin shell 35. the pebble conduit, and at least a portion of the pebble heating chamber are filled with the moving bed otpebbles. In some cases a pebble surge chamber *will b e arrangedahead of the pebble heatingchamber; When such an arrangement exists, suflicient pebbles may be supplied to fill the space above the dome in the heating chamber. Gaseous materials are injected into the lower portion of the gas heating chamber through inlet conduit 36. The gaseous materials rise through the gas heating chamber, gaining heat from the downwardly flowing pebbles, and pass rapidly out of gas heating chamber through eifluent outlet conduits 31. Pebbles which have been cooled during the gas heating step pass out of the gas heating chamber and are carried through elevator 38 to the upper portion of a heating chamber wherein they are once again subjected to the pebble heating step described above.

Gaseous 'combus'ti-- blematerials, together with'an-oxygen-contaim ing igas which 'maybe in excess of that needed to. supplyoxygen for the combustion'ofthecom- The gas heating chamber,

A pebble heatingehamber utilizing; the rafrac tory dome ofthis invention may be operated without baflle 'means'such asrefractory plate 28. Itis advantageous to use such baflie means, however. Pebbles within a pebble heating chamber form stagnant zones alongthe periphery of the bed up to anangle of about 40 to 60 from the horizontal; For'this reason a la'rgeportion of the pebbles on theside of the chamber remain within theistagnant areaand once raised to a high temperature by the rising combustion gas are-maintained at that temperature without substantially decreasing temperature of the combustion gas passing therethrough. This results in the lossof large quantities of heat by the passage from the pebble heatingchamber of combustion gas'which is still at a high temperature. It is thereforemore economical to utilize baille means whichwill-directWhe hot 'combu'stion'gas from the combustion zone into the central portion of the pebble heating chamber where the gas con tacts more'ofthe-moving 'pebblesr As the gas passes upwardly it-will tend to spread through the heating zone, thus contacting and heating those pebbles which are moving downwardly throughthe chamber.- i In some instancescombustion gas may be car+ ried from the pebble heating chamber into the gas heating chamber with the pebbles, or'conversion products may rise from the gas heating chamber, through the pebble conduit, into the pebble'heating chamber. Such an occurrence would cause the conditions ineither chamber to be unstable. For that reason it'maybe'desirable to provide conduit'means for injecting a hot gas, which'is inert to the reaction. into the pebble conduit, as a choke means. The choke means would prevent other gas from passing therethrough. a i

M Specific example a I A pebble heater apparatus, the pebble heating chamber of which is divided into heating and combustion zones, by a perforatesilicon carbide dome intermediate its ends, ,is filled with alumina pebbles of inch diameter so thatthe pebbles,

form an uninterrupted bed from the bottom of the gas heating chamber through the connecting pebble conduit a substantial spaceup into the heating zone. the dome supports about 900 pounds per square foot. I

In theoperation of the apparatus, pebbles are withdrawn from the bottom the as heating chamber and are elevated to the top of the pebble heating chamber. Methane-rich gas, together with Oxygen-containing gas, is introduced throughtangentially positioned burners into the combustionzone where it is burned. Suflicient oxygen-containing gas to substantially complete combustion of the methane-rich gas and to temper resulting combustion gas is introduced through the burners. Combustion gas which passes upwardly through the perforate dome is directed inwardly, by baffles, into the center portion of the heating chamber. Temperature of the combustion zone is maintained in the vicinity of about 2400 F. while gas issuing from the top of the pebble bed is at about 900 F. Pebbles are circulated through the apparatus at the rate of about 27 tons per hour. As the pebble pass downwardly through the gas heating chamber they give up a portion of their heat, in direct heat exchange, to gaseous materials being passed in counter-current flow thereto.

Removal of any carbon, coke or asphaltic me.-

When' the apparatus is so loaded teriai accumulations from the moving pebbles will be effected by the passage of the hot heating gas, containing an excess of oxygen, in direct heat exchange with the pebbles. Such removal of carbon or coke deposits is exothermic in reaction and by such reaction furnishes an amount of heat to the moving pebble bed.

As will be evident to those skilled in the art, various modifications of this invention can be made or followed in the light of the foregoing disclosure, discussion and example without departing from the spirit or scope of the disclosure or from the scope of the claims.

I claim:

1. In a pebble heater apparatus utilizing a moving bed of heated pebbles, an improved pebble heating chamber comprising a substantially vertically disposed closed outer shell; insulating means within and adapted so as to insulate said shell; pebble inlet means centrally disposed in the upper portion of said shell; efiiuent outlet means in the upper portion of said shell; a perforate refractory load-supporting dome within said shell, intermediate the ends of said shell and dividing the chamber within said shell into a heating zone above said dome and a combustion zone below said dome; a first pebble conduit means extending substantially centrally through said dome; a second pebble conduit means extending centrally through the bottom of said shell and upwardly into said combustion zone and enclosing a portion of said first pebble conduit therein so as to form an expansion joint therebetween, whereby said first and second pebble conduits form a pebble outlet from said heating chamber; means for separating pebbles within said heating zone from said dome; and fluid heat exchange material inlet conduit means in said shell below said dome.

2. The heating chamber of claim 1, wherein said fluid heat exchange material inlet conduit means comprises obliquely positioned burners.

3. The heating chamber of claim 1, wherein baffle means are provided over and supported by the outer portion of said perforate dome and adapted so as to direct said gas toward the axis of said chamber.

4. In a pebble heater apparatus utilizing a moving bed of heated pebbles, an improved pebble heating chamber comprising a substantially vertically disposed closed cylindrical outer shell; insulating-lining means within and adapted so as to insulate said shell; pebble inlet means centrally disposed in the upper portion of said shell; efliuent outlet means in the upper portion of said shell; a perforate dome comprising a plurality of perforate rings of super-refractory bricks, the lower perforate ring being supported on an abutment in said lining means intermediate the ends of said chamber and dividing said chamber into a heating zone above said dome and a combustion zone below said dome; a first pebble conduit means comprising a refractory throat extending substantially centrally through said dome upwardly a relatively short spaced distance into said heating zone and downwardly a short spaced distance into said combustion zone; a second pebble conduit means comprising a refractory throat extending upwardly centrally through the bottom of said shell and into said combustion zone, communicating with said first pebble conduit means by means of a slidable joint therebetween, whereby said first and second pebble conduits form a pebble outlet from said heating chamber; burners in said combustion zone, whereby combustible materials are burned within said combustion zone and hot combustion gas passes upwardly in said combustion zone, through said perforate dome; and means for separating pebbles within said heating zonefrom said dome.

5. An improved pebble heat exchange chamber comprising a substantially vertically disposed closed outer shell; pebble inlet conduit means centrally disposed in the upper portion of said,

shell; effluent outlet means in the upper end portion of said shell; a perforate refractory loadsupporting dome within said shell, intermediate the ends of said shell and dividing the chamber within said shell into upper and lower sections; centrally disposed pebble outlet conduit means extending through said dome, said lower chamber section, and the bottom of said shell; and fluid heat exchange material inlet means in said shell below said dome.

6. The heat exchange chamber of claim 5, wherein baflle means are adjacent and supported on the upper surface of said perforate dome and cover the outer portion of said dome so as to direct gaseous material passing through perforations in the outer portion of said dome inwardly toward the axis of said upper chamber section.

'7. The heating chamber of claim 1, wherein said separation means comprises a bed of aggregate material covering said dome.

LOUIS J. WEBER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,089,306 Stimmel et al Aug. 10, 1937 2,417,049 Bailey Mar. 11, 1%? 2,432,885 Hasche Dec. 16, 1947 OTHER REFERENCES Pages 116-119 inclusive of the July 1946 issue of Chemical and Metallurgical Engineering; a Pebble Heater article by C. L. Norton. Jr. 

1. IN A PEBBLE HEATER APPARATUS UTILIZING A MOVING BED OF HEATED PEBBLES, AN IMPROVED PEBBLE HEATING CHAMBER COMPRISING A SUBSTANTIALLY VERTICALLY DISPOSED CLOSED OUTER SHELL; INSULATING MEANS WITHIN ADAPTED SO ASA TO INSULATE SAID SHELL; PEBBLE INLET MEANS CENTRALLY DISPOSED IN THE UPPER PORTION OF SAID SHELL; EFFUENT OUTLET MEANS IN THE UPPER PORTION OF SAID SHELL; A PERFORATE REFACTORY LOAD-SUPPORTING DOME WITHIN SAID SHELL, INTERMEDIATE THE ENDS OF SAID SHELL AND DIVIDING THE CHAMBER WITHIN SAID SHELL IN A HEATING ZONE ABOVE SAID DOME AND A COMBUSTION ZONE BELOW SAID DOME; A FIRST PEBBLE CONDUIT MEANS EXTENDING SUBSTANTIALLY CENTRALLY THROUGH SAID DOME; A SECOND PEBLE CONDUIT MEANS EXTENDING CENTRALLY THROUGH THE BOTTOM OF SAID SHELL AND UPWARDLY INTO SAID COMBUSION ZONE AND ENCLOSING A PORTION OF SAID FIRST PEBBLE CONDUIT THEREIN SO AS TO FORM AN EXPANSION JOIN THEREBETWEEN, WHEREBY SAID FIRST AND SECOND PEBBLE CONDUITS FORM A PEBBLE OUTLET FROM SAID HEATING CHAMNBER; MEANS FOR SEPARATING PEBBLES WITHIN SAID HEATING ZONE FROM SAID DOME; AND FLUID HEAT EXCHANGE MATERIAL INLET CONDUIT MEANS IN SAID SHELL BELOW SAID DOME. 